The accessory reproductive glands of mealworm beetles will be used as model systems in which to examine general process of cell differentiation. Progressive changes in the rates of leucine incorporation into specific proteins will be considered in a context of the changing morphology, and both biochemical and morphological criteria used to identify indices of progressive differentiation, and times of differentiative transitions. The changes in patterns of protein synthesis may stem from either translational or transcriptional modulation mRNA biosynthesis will be investiated, and the character of the cellular mRNA pool will be evaluated by translational assays. Three glands will be examined: the spermathecal accessory gland of the female, the tubular accessory gland of the male, and the bean-shaped accessory gland of the male. Hormonal control of the differentiative transitions in these glands will be investigated in situ, and in culture both in vivo, and in vitro.